It is known that alkaline cleaning agents containing caustic soda, orthophosphates, condensed phosphates, silicates, complexing agents, wetting agents, and inhibitors can be used for cleaning solid material such as workpieces of metals or glass. These cleaning products are generally marketed as powdered mixtures and are delivered as such to a cleaning bath at intervals, the concentration of cleaning agent in the bath amounting to from about 0.1 to 20% by weight, dependent upon the particular application and the degree of soiling. If the cleaning solution is to be effective, the optimal concentration must be maintained. The optimal concentration may be determined by titration or by a conductivity measurement. The conductivity measurement for determining concentration may be carried out in conjunction with an automatic concentation adjustment.
One of the difficulties of using powdered products, particularly when they contain hygroscopic salts, is to ensure continuous uninterrupted introduction. In addition, it is precisly highly active, nonionic surfactants which are sensitive to solid caustic soda. During storage they change through oxidation to ether carboxylic acids, which impairs the effectiveness of the powdered products with respect to certain greases and, in the case of degreasing sprays, causes troublesome foaming.
It is also known that liquid cleaning agents showing an alkaline reaction can be used for the purpose in question, having been obtained and regenerated by combining a strongly alkaline active-substance concentrate with an acidic or neutral active-substance concentrate. However, it has not not been possible in this way to produce silicate-containing cleaners
Furthermore, products having a high active-substance content require a very high concentration of hydrotropic substance and/or of potassium salts having a low active-substance content.